Embryo Types And Characteristics Of Apomixis In Poa Pratensis L.

Poa pratensis L. is facultative apomixis plant, the embryonic development process withdifferent periods was observed to understand embryonic types and features of apomixis. Theplants studied included one commercial cultivar Baron and five wild populations fromcounties of Anding, Longxi, Qinzhou, Qingshui, Xihe, Gansu province, China. Hematoxylineosin double staining of paraffin production, whole embryo sac stain-clearing technique,callose detection etc. research method were used, combinated of polyembryony seedling rateand pattern of polyembryony seedling emergence studied apomixis of Kentucky bluegrass,which can provide theoretical basis for further understanding mechanism of apomixis.The concrete research methods and the results are as follows:The paraffin section technique with Ehrlich·s hematoxylin-eosin double stain was used toidentify the type and the characteristics of embryo in Poa pratensis L. Five embryonic typeswere observed during reproductive development process in Poa pratensis L.. The somaticapospory embryo was dominant embryo presence of them. Sexual embryo sac was typicalPolyonum type embryo sac. There were sexual embryo sac, apospory embryo sac ordiplospory embryo sac coexisting in one ovule to form polyembryony in Poa pratensis L..The polarity of the sexual embryo sac was same with synergids embryo sac，and it wasoppositive to antipodal cell embryo sac then. Somatic apospory embryo sac varied irregularlyduring it·s development, with the presence of single or more than two sacs, to developpolyembryony. It was in the majority that two embryo sacs were presented.By adopting aniline blue staining method studied accumulation of callose aroundmegasporangium and microsporocyte at reproductive process in Poa pratensis L., understanddifferences between sexual reproduction and apomixis. Accumulation of callose aroundmicrosporocyte was similar to sexual reproduction，and megasporangium developed intoembryo sac was typical Polyonum type embryo sac, the callose changing dynamics same aspocess of Polyonum type embryo sac. Diffenent types apomixis had difference callosechanging dynamics in Poa pratensis L.. Megasporangium wall between chalazal existed smallcallose in somatic apospory process, faded away with forming of somatic apospory sac; nocallose existed around megasporangium wall in generative apospory process, it is the signal ofmegasporangium meiosised unusual; small callose existed in synergids and antipodal cell formed embryo sac. By studied callose growth and decline of reproductive process in Poapratensis L., the emergence of callose means nomal meiosis.A whole embryo sac stain-clearing technique was employed to identify apomixis in Poapratensis L. following developmental process of embryo sac. The results showed thatapomictic frequency of Kentucky, Baron apomictic frequency and polyembryony rate highestin all of them, was58.7%and18.3%; and five wild populations from counties of Anding,Longxi, Qinzhou, Qingshui and Sanhe, respectively was37.6%,10.7%;47.8%,12.4%;50.2%,14.6%;47.8%,12.4%and42.1%、15.8%. There was a connection with apomictic frequencyand polyembryony rate, but not liity.Five wild Poa pratensis L.varieties in Gansu and one commercial variety Baron as trialmaterial studied germination and poly-embryo rate. The influencing factors of poly-embryoformed and the mechansim of poly-embryo seedling was studied as well. The result indicatedthat the occurrence frequency of difference varieties of leek was much difference on the basicof consistent germination rate. Among them Baron have tallest double-embryo seedlingsoccurrence frequency was14.4%, Anding wild Poa pratensis L. poly-embryo seedlings was0.92%. There are three germination types by observing polyembryony seedlings, includingone embryony seedling, two embryony seedlings and three embryony seedlings. Twoembryony seedlings had threetypes, two embryony seedlings opposite, fasciation and next, thefrenquency of fasciated embryony seedlings occurrenced highest. Three embryony seedlingshad three types, three embryony seedlings opposite, fasciation and next, the frenquency of threeembryony seedlings occurrenced infrequent, lower than hundredth. The performance ofpolyembryony seedlings involved polyembryo formation and polyembryo seedlingsgermination, the formation of polyembryo not only influenced by genetic background,polyembryony seedlings germinated also influenced by external conditions.